As a semiconductor device having a light transparent window a solid state imaging element will be described.
FIG. 6 shows a cross-section of a prior art ceramic sealed solid state imaging element. The reference numeral 1 designates a ceramic base for including a chip 6, the reference numeral 2 designates a ceramic lid, the reference numeral 3 designates low melting point glass for making the ceramic base 1 and the ceramic lid 2 adhere to the lead frame 4, the reference numeral 5 designates conductive adhesive material for fixing the chip 6, the reference numeral 7 designates a bonding wire for connecting the lead frame 4 to the terminal of the chip 6, the reference numeral 8 designates a metal cap, the reference numeral 9 designates low melting point glass, the reference numeral 10 designates light transparent glass, the reference numeral 11 designates a metal which is metallized at the aperture portion of the ceramic lid 2, and the reference numeral 12 designates a space.
The method of producing this solid state imaging element will be described.
At first, low melting point glass 3 is applied to the ceramic base 1 and the ceramic lid 2. Next, the low melting point glass 3 is melted and solidified at about 500.degree. C. such that the lead frame 4 is held between the ceramic base 1 and the ceramic lid 2 via the low melting point glass 3. After cooling, a chip 6 is fixed to the conductive adhesive material 5 in the ceramic base 1. Next, bonding wires 7 are wired so as to electrically connect the terminal of the chip 6 to the lead frame 4. Next, an element obtained by adding the light transparent glass 10 to the metal cap 8 by low melting point glass 9 is placed onto the metal 11 metallized over the surface of the aperture portion of the ceramic lid 2, whereby a space 12 is produced which is completely isolated from the outside air.
In the prior art method of producing a semiconductor device having a light transparent window such as a solid state imaging element, ceramic and metal are mainly used as constitutional material of the device, and therefore it is necessary to provide a process of melting and solidifying the low melting point glass 3 and a process of making the light transparent glass 10 adhere to the metal cap 8 by the low melting point glass 9. The production process thus becomes complicated, causing difficulty in mass producibility. Furthermore, the chip 6 is non-impervious to heat, and it is thus required to increase the size of the metal cap 8 in order to reduce the influence of heat upon welding the metal cap 8 onto the metallized metal 11, thereby resulting in a disadvantage that the sealed size becomes unecessary large.